The present invention is in the technical field of oral healthcare and dental application. More particularly, the present invention is in restorative dentistry for tooth enamel loss.
There is no natural regeneration for tooth enamel and no current methods have proven successful, safe, or cost effective to re-form the enamel layer once damaged. Ameloblasts—the living cells present in the initial formation of the tooth enamel layer—are no longer present in mature enamel (Wei, Jie, Wang, Jiecheng, Shan, Wenpeng,. “Development of a Fluorapatite Cement for Dental Enamel Defects Repair”, Springer Science+Business Media, Center for Biomedical Materials and Tissue Engineering, Beijing. Web). Therefore, in mature enamel there are no living cells to perform repair when the enamel layer is damaged. Dental caries (cavities) and erosion of enamel leave the dentine layer permanently exposed and subject to further caries.
From doing background research, I learned why replicating enamel's natural structure that bonds to the dentin layer has proven difficult. Tooth enamel's known composition is hydroxyapatite. The hydroxyapatite compound, Ca10(PO4)6(OH)2, can be easily synthesized in the lab but the result, as I discovered, is a chalky white paste without bonding ability (Hannig, Matthias. “Nanomaterials in Preventative Dentistry.” Nature NanoTechnology Vol. 5, Aug 2010 at nature with the extension .com/naturenanotechnology of the world wide web). The resulting powder has no bonding ability. Without bonding ability, hydroxyapatite alone cannot reform the dentin enamel junction (DEJ), and cracks would penetrate tooth dentin directly.
The structure of enamel and its strong bond to the dentin layer has proven difficult to artificially replicate. Enamel is composed of hydroxyapatite (HA), the “main biomineral component of human hard tissues . . . its stoichiometry represented by the formula Ca10(PO4)6(OH)2” (Oliveira, Marise and Mansur, Herman. “Synthetic Tooth Enamel: SEM Characterization of a Fluoride Hydroxyaoatite Coating for Dentistry Applications”. Mat. Res. Web. 2007).The biocompatible material of HA can be easily synthesized in the lab producing the HA paste which is a mixture of calcium hydrogen phosphate hydrate—Ca(H2PO4)—H2O, and calcium hydroxide—Ca(OH)(Yamagishi K., Onuma K., Suzuki T., Okada F. “Materials Chemistry: A Synthetic Enamel for Rapid Tooth Repair’, Nature, 433, 7028, p. 819, Science Reference Center, EBSCOhost. at <http with the extension web.ebscohost.com/scirc/detail? sid=11a81209 of the world wide web>). However, the HA material results is a chalky white powder which will not adhere to the tooth because the HA alone has no bonding ability. The HA crystal's observed in true enamel are “organized spatially into rod and interrod territories as they form” (Smith, C. E. “Cellular and Chemical Events During Enamel Maturation.” Critical Reviews in Oral Biology and Medicine. 15.6 (2004): at cro with the extension.sagepub.com/content/9/2/128 of the world wide web). The rod bond structure suggests a bonding agent is required in conjunction with HA paste to re-create enamel bond structure.
The junction between enamel and dentin, called the dentin-enamel junction (DEJ), is known for its unique “biomechanical properties that provide a crack-arrest barrier for flaws formed in the brittle enamel” (Ritchie, R., et al. “The Dentin-Enamel Junction and the Fracture of Human Teeth.” Nature Materials 4.3(2005): 229. Science Reference Center. at web with the extension .ebscohost.com/sc of the world wide web). Dentin is the “main bony part of a tooth beneath the enamel, surrounding the pulp chamber and root canals” (“Dentin.” American Heritage Student Science Dictionary (2009): 95. Science Reference Center. at Web. Sept. 2012. see web with the extension .ebscohost.com/etc of the world wide web). When bonding re-created enamel, it is important to consider the critical role of the DEJ region which “prevents cracks from forming in enamel, traversing the interface, and causing catastrophic tooth fractures” (Ritchie, R., et al. “The Dentin-Enamel Junction and the Fracture of Human Teeth.” Nature Materials 4.3(2005): 229. Science Reference Center. at web with the extension .ebscohost.com/sc of the world wide web). The DEJ, in essence, serves like padding in a helmet; enamel is the hard, outer helmet shell and dentin the head beneath the padding. Upon impact, the padding will cushion the outer enamel shell, preventing fractures to the enamel and underneath dentin layers.
Ceramics, polymer composites, and amalgams that are currently used to refill cavity gaps cannot provide the layer of protection that only a true enamel coating is capable of doing (Hannig, Matthias. “Nanomaterials in Preventative Dentistry.” Nature NanoTechnology Vol. 5, Aug 2010 at nature with the extension .com/naturenanotechnology of the world wide web). In vitro experiments have shown that the use of Hydroxyapatite “nanocrystals interact with bacterial adhesion and binding of microorganisms to tooth surface,” (Smith, C. E. “Cellular and Chemical Events During Enamel Maturation.” Critical Reviews in Oral Biology and Medicine. 15.6 (2004): n. page.http:// with the extension cro.sagepub.com/content/9/2/128 of the world wide web) therefore decreasing risk of enamel loss and subsequent cavities. The health significance of re-creating the enamel layer would include shielding the tooth against cavities, providing an insulation barrier for the teeth against temperature changes, protecting teeth in daily use during chewing, biting, and grinding, and decreasing risks associated with enamel loss such as gum disease—which affects eighty percent of adults—and decreasing risks correlated with more serious diseases resulting from oral complications.
Research was done to determine if there were similar patents that would provide a method description for the creation of an enamel solution for teeth and application.
U.S. Pat. No. 4,080,440, entitled Method for Reminieralizing Tooth Enamel, details a process for forming a “metastable mixture by mixing a solution containing a soluble calcium salt with a solution containing a soluble phosphate salt.” This patent presents a solution that maintains the condition of natural enamel through a mouthwash but does not repair damaged enamel.
My created enamel replicates the physical and structural characteristics of natural enamel and does not ‘maintain’ current enamel, but would replace the enamel layer providing a natural coat. A solution of ‘calcium ion and phosphate ion’ alone cannot provide bonding ability to the dentin layer. However, as observed through my chemical composition with a biologically compatible bonding agent, a suitable enamel that bonds to the dentin layer is created.
U.S. Pat. No. 4,645,456 entitled Adhesive Compositions for Tooth Enamel details “a system for bonding of dental filling composites and orthodontic adhesives to tooth enamel.” The process is an alternative method for highly acidic tooth etching prior to fillings.
The adhesive composites described to prepare for tooth etching are irrelevant, in the case of my invention, since teeth with enamel loss would not need etching prior to the application of my created enamel solution. The bonding agent and composition of my created enamel has been observed in the lab to have bonding ability capable to bond to surrounding enamel without etching.
U.S. Pat. No. 3,679,360 entitled Process for the Preparation of Brushite Crystals details “a process for preparation of calcium phosphate salts wherein a calcium phosphate salt is deposited from a gel medium onto the surface of a tooth . . . used to strengthen weak or damaged teeth.” The surface on which apatite growth is desired must be prepared (as by roughening), and the tooth and coatings must be covered by a suitable cap for several days while the mineralization of the tooth's surface occurs.
The gel medium used to deposit the said calcium phosphate solution is applied to teeth directly, and used to “strengthen” teeth. My created enamel would not “strengthen” teeth, but when applied would repair by replacing the damaged enamel layer on teeth and provide a new, structurally identical enamel covering. The medium would be a paste rather than gel and the application time frame would be significantly less for my created enamel due to the bonding agent used (containing polymerization properties).
U.S. Pat. No. 4,083,955 entitled Process and Compositions for Reminerlzation of Dental Enamel details “a calcium and phosphate ion sequentially applied to dental enamel resulting in remineralization of subsurface dental enamel.” The process explained precipitates hydroxyapatite and is combined with indium and fluoride ions creating a ZnNH4PO4. The only considerable similarity: ZnNH4PO4 created in the process patented in 4,083,955, although containing an apatite, does not result in the same formula created through my process: Ca10(PO4)6(OH)2(s)+HEMA+H2O(1).